Tax refunds matter to household finances. That's the clear message from a recent study by the JPMorgan Chase & Co. Institute. The report draws on a large data set of Chase bank transactions and one million families from 2015 to 2017. (In other words, before the new tax law took effect in 2018.)

"Our findings underscore the fact that, whether by design or not, the tax system is a primary tool by which many families generate lump sums of cash," wrote the study's authors.

They found most families receive refunds. The average refund of $3,602 represented almost six weeks' income. No wonder people worry that their refunds could be smaller than expected under the new law. (To be sure, paychecks were slightly larger in 2018 if people did not adjust withholding, affecting potential refunds.)

The reliance on refunds has caused much disapproving commentary. The Trump administration seems concerned people are confusing a smaller refund with a tax increase. The personal-finance industry has chided people for their "irrational" practice of withholding too much from their paychecks. Yet the reliance on the tax system emphasizes how hard it is for families to save, for which there are many reasons. For one, household incomes have stagnated for years. Also, children, homes and health insurance add expensive household costs.

So families have figured out a convenient, simple and automatic system to set aside money during the year: withholding it. Of course, the professionals are right to point out better ways to save. That doesn't mean this is a bad option. The larger personal finance point is that people often find ways to manage their money that don't meet the textbook definition of smart money moves. But they work for the demands of their everyday lives.

That's one theme of "The Financial Diaries: How American Families Cope in a World of Uncertainty," by scholars Jonathan Morduch and Rachel Schneider. The book tells stories of people like Mike, who lives barely above the poverty line and rarely spends more than $20 at a time. Mike buys his groceries and gas with cash. He keeps $100 in his wallet and more than that in two envelopes at home — one for property taxes and the other a general fund. "Knowing his exact balance and spending in small amounts is important for him to keep his spending within his budget," they wrote.

Instead of lectures about irrational behavior and calls for financial literacy, how about systemwide options that make savings easy, convenient and automatic?

Chris Farrell is senior economics contributor for "Marketplace" and commentator for Minnesota Public Radio.